NEW YORK: Verizon has joined the list of major advertisers telling their agencies that they must diversity their workforce or risk losing their business.

In a letter sent to 11 agencies on September 16, CMO Diego Scotti described diversity as "an explicit business objective," according to The New York Times. The agencies have one month to submit details on their female and minority staff numbers, and must then submit "action plans" for increasing those numbers.

Early last month, HP and General Mills both told their agencies that they must improve the diversity of their workforce or risk losing their business. Those directives both came with specific goals for female and minority employment, though the Verizon letter did not.

"Marketers are expected to have a deep understanding and insight about their markets, about decision makers, and about customers," Mr. Scotti said in the letter, which can be read here. "We are more likely to create solutions that amaze our customers if our workforce and suppliers represent the communities we serve."

Verizon's ad agencies include McCann Erickson, Wieden & Kennedy, and McGarryBowen; it works with Weber Shandwick on PR. The company is one of the biggest advertisers in the U.S., spending $1.3 billion on ads in both 2014 and 2015, according to Kantar Media.